JP5727643B1 - Piston ring and reciprocating compressor - Google Patents

Abstract

A piston ring having excellent sealing performance and a reciprocating compressor having excellent sealing performance and capable of efficiently compressing gas are provided. A piston ring (1) includes a first ring (5) and a second ring (6) arranged to overlap in the piston axial direction. The second ring 6 is disposed on the high pressure side of the first ring 5 in the piston axial direction. The first ring 5 includes a pressed surface 512 that faces the second ring 6 and approaches the second ring 6 side in the piston axial direction as it goes outward in the radial direction. The second ring 6 includes a pressing surface 641 that faces the first ring 5 and comes into contact with the pressed surface 512 and approaches the first ring 5 side in the piston axial direction as it goes radially inward. A low pressure groove 642 that leads to the joint 50 of the first ring 5 is formed on the pressing surface 641. [Selection] Figure 1

Description

  The present invention relates to a piston ring mounted on an outer peripheral surface of a piston and a reciprocating compressor including the same.

  Conventionally, piston rings are used in reciprocating compressors, piston engines, and the like to prevent gas in the cylinder from leaking between the piston and the cylinder.

  For example, Patent Document 1 discloses a piston ring composed of a first ring and a second ring. The first ring and the second ring are mounted in a ring groove formed on the outer peripheral surface of the piston in a state where they are stacked in two stages. Both the first ring and the second ring have joints, and are arranged in the ring groove in a state where the mutual joints are shifted in the circumferential direction of the piston.

JP 2004-36837 A

  By the way, the piston ring disclosed by patent document 1 presses the ring arrange | positioned at the high voltage | pressure side among the 1st ring and the 2nd ring, and both rings contact | adhere. However, the adhesiveness of both rings is low and the sealing performance is not high.

  Both rings are pressed against the inner peripheral surface of the cylinder by the high-pressure gas that has entered the inner part of the ring groove. However, this pressing force cannot be said to be large, and gas leakage may occur from between the piston ring and the inner peripheral surface of the cylinder. Also in this respect, the sealing performance is not high.

  Therefore, an object of the present invention is to provide a piston ring having high sealing performance and a reciprocating compressor having high sealing performance between a piston and a cylinder and capable of efficiently compressing gas.

  In order to solve the above-mentioned object, a piston ring according to a first aspect of the present invention includes a first ring and a second ring that are arranged to overlap each other in the piston axial direction, and the second ring is the first ring in the piston axial direction. The first ring includes a pressed surface that approaches the second ring side in the piston axial direction toward the second ring toward the outer side in the radial direction. The two rings include a pressing surface that faces the first ring and comes into contact with the pressed surface toward the inner side in the radial direction toward the first ring side in the piston axial direction. A low pressure groove leading to the joint is formed.

  According to a second aspect of the present invention, in the piston ring according to the first aspect, a protrusion that is fitted into the low pressure groove is formed on the pressed surface.

  The invention according to claim 3 is the piston ring according to claim 1 or 2, wherein the low-pressure groove extends in the circumferential direction of the second ring, and both end portions thereof face the joint of the second ring. So as not to open.

  The reciprocating compressor of the invention according to claim 4 is a reciprocating compressor that compresses the gas sucked into the compression chamber of the cylinder with the piston in the cylinder, and a ring groove is formed on the outer peripheral surface of the piston, The piston ring according to any one of claims 1 to 3 is provided in the ring groove, and the second ring of the piston ring is disposed so as to overlap the compression chamber side of the first ring.

  In the piston ring of the present invention, the first ring has a pressed surface. The pressed surface approaches the second ring in the piston axial direction as it faces the second ring and goes radially outward. For this reason, when the second ring is pressed to the low pressure side by the high pressure side gas in the cylinder when the piston is driven, the first ring is pressed radially outward by the second ring. For this reason, the first ring comes to be pressed against the inner peripheral surface of the cylinder with a large force. Accordingly, the sealing performance can be improved.

  In addition, a low pressure groove communicating with the joint of the first ring 5 is formed on the pressing surface facing the first ring of the second ring. For this reason, when the piston is driven, the gas on the low pressure side in the cylinder enters the low pressure groove of the second ring through the abutment of the first ring, and the pressure in the low pressure groove becomes low, thereby pressing the first ring. The surface is pressed with a large force by the pressing surface of the second ring, and the pressed surface and the pressing surface come into close contact with each other. Therefore, the sealing performance can be further improved.

  In the invention according to claim 2, when the first ring tries to move in the radial direction with respect to the second ring, the protrusion is caught by the second ring, whereby the first ring is moved relative to the second ring. Thus, it is prevented from moving in the radial direction. For this reason, the first ring and the second ring move integrally in the radial direction, and the first ring and the second ring are easily worn evenly.

  In the invention according to claim 3, the high-pressure side gas in the cylinder is difficult to enter the low-pressure groove through the joint of the second ring, and the pressure in the low-pressure groove can be made sufficiently low. For this reason, the pressed surface of the first ring and the pressing surface of the second ring are more easily adhered, and the sealing performance can be further improved.

  In the invention according to claim 4, the piston ring can prevent the gas on the compression chamber side from leaking to the low pressure side. For this reason, the gas in a compression chamber can be compressed efficiently.

It is an expanded sectional view near the piston ring of the reciprocating compressor provided with the piston ring according to the first embodiment. It is a disassembled perspective view of the piston ring. (A) is a top view of the 1st ring of the said piston ring, (b) is a partially notched front view of the said 1st ring. It is sectional drawing in the AA line of Fig.3 (a). (A) is a top view of the second ring of the piston ring, (b) is a partially cutaway front view of the second ring, and (c) is a bottom view of the second ring. It is a piping system diagram of the reciprocating compressor. It is a longitudinal cross-sectional view of the compression part of the high stage side of the said reciprocating compressor. It is a bottom view of the 2nd ring of a 2nd embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
First, the first embodiment will be described. The piston ring 1 according to this embodiment is attached to a piston 81 (see FIG. 7) of a reciprocating compressor 2 described later.

  FIG. 1 is a cross-sectional view of a main part of a reciprocating compressor 2 in which a piston ring 1 is mounted on a piston 81. In FIG. 1, 80 is a cylinder.

  Hereinafter, the axial direction of the piston 81 is referred to as a piston axial direction, and the piston ring 1 will be described with reference to the direction in which the piston 81 is mounted. Also, the compression chamber 802 side (the direction indicated by D1 in FIG. 1) that is the distal end side of the piston 81 in the piston axial direction is defined as the high pressure side, and the compression chamber 802 side that is the proximal end side of the piston 81 in the piston axial direction. The opposite side (direction indicated by D2 in FIG. 1) is defined as the low pressure side.

  As shown in FIG. 2, the piston ring 1 includes a first ring 5 and a second ring 6. The first ring 5 and the second ring 6 are disposed so as to overlap in the piston axial direction, and the second ring 6 is disposed on the high pressure side of the first ring 5.

  The material of the first ring 5 and the second ring 6 is a self-lubricating synthetic resin such as PTFE (polytetrafluoroethylene), difluidized molybdenum, PEEK (polyetheretherketone), or these resins and carbon or carbon fiber. It is a composite material.

  As shown in FIG. 3A, the first ring 5 is formed with a joint 50 that divides a part of the circumferential direction.

  The first ring 5 includes a circular ring-shaped main portion 51 as viewed from the piston axial direction, and a protrusion 52 protruding from the main portion 51 toward the second ring 6. As shown in FIG. 3B, the cross-sectional shape orthogonal to the circumferential direction of the main portion 51 is a right triangle.

  The main portion 51 includes a low pressure side surface 510, an outer peripheral surface 511, and a pressed surface 512. The low pressure side surface 510 faces the side opposite to the second ring 6 side and is orthogonal to the piston axial direction.

  The outer peripheral surface 511 forms a circular ring shape when viewed from the piston axial direction, and is parallel to the piston axial direction. An end edge of the outer peripheral surface 511 opposite to the second ring 6 is connected to the outer peripheral edge of the low-pressure side surface 510. The length of the outer peripheral surface 511 in the piston axial direction is smaller than the width of the low pressure side surface 510, and the cross section of the main portion 51 is long in the direction orthogonal to the piston axial direction.

  The pressed surface 512 has an inner peripheral edge connected to the inner peripheral edge of the low-pressure side surface 510 and an outer peripheral edge connected to the edge of the outer peripheral face 511 on the second ring 6 side. The pressed surface 512 is configured by an inclined surface that is inclined so as to approach the second ring 6 side in the piston axial direction as going outward in the radial direction, and has a tapered shape.

  As shown in FIG. 3A, the protrusion 52 includes a protrusion 520 that extends in the circumferential direction of the main portion 51. The protrusion 52 of this embodiment is composed of two protrusions 520. The protrusion 520 </ b> A which is one protrusion 520 is continuously formed in a range from one end surface 514 of the main portion 51 facing the joint 50 to a portion 516 opposite to the joint 50. The ridge 520B, which is the other ridge 520, is formed continuously in a range from the other end surface 515 of the main portion 51 to the front of the portion 516 on the opposite side to the joint 50. In other words, the protrusion 52 is divided at two locations of the abutment 50 and the portion 516 opposite to the abutment 50 in the circumferential direction of the first ring 5. Hereinafter, the portion 516 opposite to the joint 50 of the main portion 51 of the first ring 5, that is, the portion 516 where the protrusion 520 is not formed, located between both protrusions 520 in the circumferential direction of the first ring 5. Is referred to as an abutment cover 516.

  Each protrusion 520 is formed at an intermediate portion in the width direction of the pressed surface 512. As shown in FIG. 1, each protrusion 520 has a semicircular shape in which a cross-sectional shape perpendicular to the circumferential direction of the first ring 5 is convex toward the second ring 6 side.

  The second ring 6 is disposed so as to overlap the high pressure side of the first ring 5. As shown in FIG. 5A, the second ring 6 is formed with a joint 60 that divides a part of the circumferential direction. The joint 60 is a right-angle joint, and both end faces 67 and 68 of the second ring 6 are orthogonal to the circumferential direction of the second ring 6. The joint 50 of the first ring 5 and the joint 60 of the second ring 6 may be a diagonal joint or a stepped joint.

  The abutment 60 of the second ring 6 is arranged at a position shifted from the abutment 50 of the first ring 5 by approximately 180 degrees in the circumferential direction. The joint 60 of the second ring 6 is disposed on the high pressure side of the joint cover 516 of the first ring 5 and is covered by the joint cover 516. The abutment cover 516 of the first ring 5 is longer in the circumferential direction than the abutment 60 of the second ring 6. For this reason, even if the second ring 6 is worn and the joint 60 of the second ring 6 becomes somewhat larger, the joint 60 is covered with the joint cover 516.

  As shown in FIG. 5B, the second ring 6 has a shorter length in the piston axial direction toward the outer side in the radial direction. The second ring 6 includes a high pressure side surface 61, an outer peripheral surface 62, an inner peripheral surface 63, and a low pressure side surface 64.

  The high pressure side surface 61 faces the side opposite to the first ring 5. The high pressure side surface 61 includes an outer portion 610, an inner portion 611, and a step surface 612. The outer portion 610 and the inner portion 611 are orthogonal to the piston axial direction. The inner part 611 falls to the lower pressure side than the outer part 610. The outer peripheral edge of the inner portion 611 and the inner peripheral edge of the outer portion 610 are connected via a step surface 612. The step surface 612 is parallel to the piston axial direction. A notch 66 surrounded by an inner portion 611 and a step surface 612 is formed on the inner side in the radial direction of the outer portion 610.

  The outer peripheral surface 62 and the inner peripheral surface 63 form a concentric circular ring shape when viewed from the piston axial direction, and are parallel to the piston axial direction. The outer circumferential surface 62 is shorter in the piston axial direction than the inner circumferential surface 63. The edge of the outer peripheral surface 62 opposite to the first ring 5 side is connected to the outer peripheral edge of the outer portion 610 of the high-pressure side surface 61. The edge of the inner peripheral surface 63 opposite to the first ring 5 side is connected to the inner peripheral edge of the inner portion 611 of the high-pressure side surface 61.

  The low pressure side face 64 faces the first ring 5. The low-pressure side surface 64 includes an inner portion 640 and a pressing surface 641 located on the radially outer side of the inner portion 640. The inner portion 640 constitutes the radially inner end of the low pressure side surface 64. The inner portion 640 is orthogonal to the piston axial direction. The inner peripheral edge of the inner portion 640 is connected to the edge of the inner peripheral surface 63 on the first ring 5 side.

  The pressing surface 641 has an inner peripheral edge connected to the outer peripheral edge of the inner portion 640, and an outer peripheral edge connected to the edge of the outer peripheral surface 62 on the first ring 5 side. The pressing surface 641 is configured by an inclined surface that is inclined so as to approach the first ring 5 side in the piston axial direction as it goes radially inward, and has a tapered shape. The pressing surface 641 is parallel to the pressed surface 512 of the first ring 5. Further, the pressing surface 641 and the pressed surface 512 have substantially the same width.

  A low pressure groove 642 extending in the circumferential direction of the second ring 6 is formed in the pressing surface 641. As shown in FIG. 5C, the low-pressure groove 642 is formed continuously from one end portion to the other end portion in the circumferential direction of the second ring 6, and has an arc shape when viewed from the first ring 5 side. . Both end portions 644 and 645 in the length direction of the low-pressure groove 642 are in front of the both end faces 67 and 68 facing the joint 60 of the second ring 6 in the circumferential direction of the second ring 6 (on the opposite side to the joint 60 side). It is located and does not open from both end faces 67 and 68. That is, both ends 644 and 645 of the low pressure groove 642 are not open and do not communicate with the joint 60.

  The low pressure groove 642 is formed in an intermediate portion of the pressing surface 641 in the width direction. As shown in FIG. 1, the cross-sectional shape of the low-pressure groove 642 is a semicircular shape that is slightly larger than the protrusion 52.

  As shown in FIG. 1, a ring groove 810 having a U-shaped cross section is formed in the circumferential direction on the outer circumferential surface 811 of the piston 81 to which the piston ring 1 is mounted. The piston ring 1 is attached to the piston 81 by, for example, fitting the second ring 6 into the ring groove 810 and then fitting the first ring 5 into the ring groove 810 from the outside in the radial direction of the second ring 6. . At this time, the protrusion 52 (the protrusions 520 </ b> A and 520 </ b> B) of the first ring 5 is fitted into the low pressure groove 642 of the second ring 6.

  As described above, when the first ring 5 is fitted into the ring groove 810, the protrusion 52 of the first ring 5 gets over the outer portion 643 of the pressing surface 641 of the second ring 6 than the low pressure groove 642, and the low pressure groove 642. Need to be fitted. Here, the notch 66 of the second ring 6 forms a gap for allowing deformation of the second ring 6 when the outer portion 643 is pushed in by the protrusions 520A and 520B. For this reason, the first ring 5 can be easily fitted into the ring groove 810.

  In a state where the piston ring 1 is mounted on the piston 81, the pressing surface 641 of the second ring 6 comes into surface contact with the pressed surface 512 of the first ring 5, as shown in FIG. Further, the low pressure side surface 510 of the first ring 5 and the low pressure side surface 64 of the second ring are close to and opposed to the low pressure side surface of the ring groove 810, and the outer portion 610 of the high pressure side surface 61 of the second ring is the high pressure side of the ring groove 810. Proximity to the side surface. Further, the outer ends of the first ring 5 and the second ring 6 protrude radially outward from the outer peripheral surface 811 of the piston 81, and the outer peripheral surface 511 of the first ring 5 and the outer peripheral surface 62 of the second ring 6 are Due to the proximity of the inner peripheral surface 800 of the cylinder 80, the piston ring 1 seals the space between the inner peripheral surface 800 of the cylinder 80 and the outer peripheral surface 811 of the piston 81 when the piston 81 is driven.

  In a state where the piston ring 1 is mounted on the piston 81, the protrusion 52 of the first ring 5 is fitted into the low pressure groove 642 of the second ring 6. For this reason, when the first ring 5 is about to move in the radial direction with respect to the second ring 6, the protrusion 52 of the first ring 5 is caught on the second ring 6, and the first ring 5 is moved to the second ring 6. In contrast, movement in the radial direction is restricted.

  In addition, an end 521 (see FIG. 3A) on the opposite side to the joint 50 in the longitudinal direction of one protrusion 520 </ b> A of the first ring 5 is an end 644 in the longitudinal direction of the low-pressure groove 642 of the second ring 6. The end 522 (see FIG. 3A) on the opposite side to the joint 50 in the longitudinal direction of the other protrusion 520B of the first ring 5 is arranged in the low pressure of the second ring 6 (see FIG. 5C). It arrange | positions at the other end part 645 (FIG.5 (c)) of the longitudinal direction of the groove | channel 642. FIG. For this reason, when the first ring 5 tries to move in the circumferential direction with respect to the second ring 6, either one of the protrusions 520 </ b> A and 520 </ b> B is in the longitudinal direction of the low-pressure groove 642. The first ring 5 is restricted from moving in the circumferential direction with respect to the second ring 6 by hitting the joint cover 516 constituting the corresponding end surface. As a result, the joint 50 of the first ring 5 and the joint 60 of the second ring 6 are prevented from overlapping each other and the sealing performance is prevented from being lowered.

  When the piston 81 is driven, the high-pressure gas in the cylinder 80 enters the high-pressure side and the radially inner side of the second ring 6 in the ring groove 810, and the second ring 6 is caused to enter the low-pressure side and the radially outer side by this high-pressure gas. Pressed. Accordingly, the pressed surface 512 of the first ring 5 is pressed by the pressing surface 641 of the second ring 6.

  As shown in FIG. 1, the pressed surface 512 facing the second ring 6 of the first ring 5 is inclined so as to approach the first ring 5 side in the piston axial direction as it goes inward in the radial direction. For this reason, when the second ring 6 is pressed to the low pressure side by the high-pressure gas, the first ring 5 is also pressed radially outward by this force. For this reason, the first ring 5 is pressed against the inner peripheral surface 800 of the cylinder 80 with a large force, and excellent sealing performance is ensured.

  When the piston ring 1 is mounted on the piston 81, the second ring 6 is interposed between the protrusion 52 (the protrusions 520 </ b> A and 520 </ b> B) of the first ring 5 and the inner surface of the low-pressure groove 642 of the second ring 6. A gap 10 is formed which leads to the joint 60, and the gap 10 communicates with the joint 50 of the first ring 5 at an intermediate portion in the length direction of the low pressure groove 642.

  For this reason, when the piston 81 is driven, the gas on the low pressure side in the cylinder 80 enters the gap 10 formed in the low pressure groove 642 of the second ring 6 through the joint 50 of the first ring 5. As a result, the pressure in the gap 10 becomes lower than the pressure between the second ring 6 and the ring groove 810. For this reason, the pressed surface 512 of the first ring 5 is pressed by the pressing surface 641 with a large force, the pressed surface 512 and the pressing surface 641 are in close contact, and the sealing performance is further enhanced.

  When the piston 81 is driven, the first ring 5 and the second ring 6 slide on the inner peripheral surface 800 of the cylinder 80. For this reason, when the piston 81 is driven for a long time, the radially outer end of the first ring 5 and the radially outer end of the second ring 6 are worn. Here, when the piston 81 is driven, the pressure between the first ring 5 disposed on the low pressure side and the inner peripheral surface 800 of the cylinder 80 is the second ring 6 disposed on the high pressure side and the inner periphery of the cylinder 80. It becomes lower than the pressure between the surface 800 and the differential pressure with the high-pressure gas that has entered the ring groove 810 increases. For this reason, the first ring 5 is pressed against the inner peripheral surface 800 of the cylinder 80 with a force larger than that of the second ring 6, and the first ring 5 is more easily worn than the second ring 6. However, in the piston ring 1 of the present embodiment, the length of the outer peripheral surface 62 of the second ring 6 in the piston axial direction is shorter than the length of the outer peripheral surface 511 of the first ring 5 in the piston axial direction. The radially outer end of the two ring 6 is more easily worn than the radially outer end of the first ring 5. Accordingly, it is possible to evenly wear the first ring 5 and the second ring 6, thereby extending the life of the piston ring 1.

  FIG. 6 shows an overall configuration of a reciprocating compressor 2 provided with the piston ring 1 of the present embodiment. The reciprocating compressor 2 is a two-stage reciprocating compressor, and includes a low-stage side compression unit 7 and a rear-stage side compression unit 8.

  The low-stage compression unit 7 includes a cylinder 70 and a piston 71 provided in the cylinder 70 so as to be slidable back and forth. The cylinder 70 includes a compression chamber 700. The compression unit 7 sucks gas into the compression chamber 700 by reciprocating sliding of the piston 71 and compresses it to a predetermined pressure. The gas thus compressed is stored in the tank 92 through the communication passage 91 and maintained at a predetermined pressure (for example, 35 MPa).

  The compression unit 8 on the higher stage side includes a cylinder 80 and a piston 81 provided in the cylinder 80 so as to be able to reciprocate. As shown in FIG. 7, the cylinder 80 includes a cylinder main body 803 in which a compression chamber 802 is formed, and a cylindrical cylinder liner 801 that is fitted and fixed inside the cylinder main body 803. An inner peripheral surface 800 of the cylinder 80 is constituted by a cylinder liner 801. And the piston ring 1 of this embodiment is mounted | worn with the piston 81 with which this high stage side compression part 8 is provided.

  The high-stage compression unit 8 sucks compressed gas stored in the tank 92 into the compression chamber 700 through the communication passage 93 by reciprocating sliding of the piston 81, and compresses this gas to one-stage high pressure (for example, 100 MPa). To do. The compressed gas compressed by the compression unit 8 is sent out through the delivery passage 94. The delivery passage 94 is provided with a cooler 95 (see FIG. 6) for cooling the compressed gas compressed by the compression unit 8.

  6 includes a piston rod 900 having one end connected to the base end of a piston 81, and the other end of the piston rod 900 connected to the inside of the guide cylinder 901. A cross head 902 that is reciprocally mounted on the head, a connecting rod 903 having one end connected to the cross head 902, and a crankshaft 905 that is connected to the other end of the connecting rod 903 and is rotatably supported by the crankcase 904. And a drive motor 907 connected to the crankshaft 905 via a power transmission mechanism 906 composed of a pulley and a belt so as to be able to transmit power. The drive unit 90 drives the drive motor 907 to cause rotation of the crankshaft 905 and reciprocation of the cross head 902 in the guide cylinder 901, and finally reciprocation of the piston 81 in the cylinder 80. Let

  Although not shown, the drive unit that drives the lower-stage compression unit 7 is the same as the drive unit 90 that drives the subsequent-stage compression unit 8. The drive unit that drives the low-stage compression unit 7 may have a structure different from that of the drive unit 90. Further, the drive unit that drives the low-stage compression unit 7 may have the same drive source as that of the drive unit 90.

  In FIG. 6, 96 is a gas introduction passage for introducing the gas in the tank 92 into the cylinder 80. In FIG. 6, reference numeral 97 denotes a return passage for returning the compressed gas leaked from the compression chamber 802 side of the cylinder 80 to the crankcase 904 side to the suction side of the low-stage compression unit 7. In FIG. 6, reference numeral 98 denotes a filter provided in the return passage 98.

  In the piston ring 1 of the present embodiment described above, the first ring 5 includes the pressed surface 512 that faces the second ring 6, and the more the pressed surface 512 goes radially outward, the more the first ring 5 moves in the piston axial direction. Approaching 2 ring 6 side. For this reason, when the second ring 6 is pressed to the low pressure side by the high-pressure side gas in the cylinder 80 when the piston 81 is driven, the first ring 5 is brought into contact with the inner peripheral surface 800 of the cylinder 80 by the second ring 6. It comes to be pushed outward in the existing radial direction. For this reason, the first ring 5 is pressed against the inner peripheral surface 800 of the cylinder 80 with a large force, and the sealing performance can be improved. In addition, a low pressure groove 642 that communicates with the joint 50 of the first ring 5 is formed on the pressing surface 641 that faces the first ring 5 of the second ring 6. For this reason, when the piston 81 is driven, the low-pressure side gas in the cylinder 80 enters the low-pressure groove 642 of the second ring 6 through the joint 50 of the first ring 5, and the inside of the low-pressure groove 642 becomes low pressure. For this reason, the pressed surface 512 of the first ring 5 is pressed with a large force by the pressing surface 641 of the second ring 6, and the pressed surface 512 and the pressing surface 641 are firmly adhered. For this reason, the sealing performance can be further improved.

  In addition, the pressed surface 512 is preferably formed with a protrusion 52 that is fitted into the low-pressure groove 642 as in the present embodiment. In this way, when the first ring 5 is about to move in the radial direction with respect to the second ring 6, the protrusion 52 is caught by the second ring 6, and the first ring 5 is brought into contact with the second ring 6. In contrast, movement in the radial direction is prevented. For this reason, the 1st ring 5 and the 2nd ring 6 are united, and it becomes easy to wear the 1st ring 5 and the 2nd ring 6 equally.

  Further, as in the present embodiment, the piston ring 1 has a low-pressure groove 642 extending in the circumferential direction of the second ring 6 so that both ends thereof do not open from both end faces 514 and 515 facing the joint 60 of the second ring 6. Preferably it is formed. By doing in this way, it becomes difficult for the high-pressure side gas in the cylinder 80 to enter the low-pressure groove 642 via the joint 60 of the second ring 6, and the pressure in the low-pressure groove 642 can be made sufficiently low. For this reason, the pressed surface 512 of the first ring 5 and the pressing surface 641 of the second ring 6 are more closely attached.

  Moreover, the reciprocating compressor 2 of the present embodiment has the following configuration. In other words, the reciprocating compressor compresses the gas sucked into the compression chamber 802 of the cylinder 80 by the piston 81 in the cylinder 80. A ring groove 810 is formed on the outer peripheral surface 811 of the piston 81. The piston ring 1 is provided in the ring groove 810, and the second ring 6 of the piston ring 1 is disposed so as to overlap the compression chamber 802 side of the first ring 5. The reciprocating compressor 2 having this configuration can prevent the gas on the compression chamber 802 side from leaking to the low pressure side by the piston ring 1 described above, and can efficiently compress the gas in the compression chamber 802. .

  In the present embodiment, the protrusion 52 is provided on the first ring 5 of the piston ring 1, but the protrusion 52 may be omitted. In this way, when the piston ring 1 is mounted on the piston 81, the operation of fitting the first ring 5 into the ring groove 810 after fitting the second ring 6 into the ring groove 810 of the piston 81 is facilitated.

(Second Embodiment)
Next, a second embodiment will be described. In the following description, the same components as those in the above embodiment are given the same numbers, and redundant descriptions are omitted.

  By the way, if the sealing performance of the piston ring 1 is too high, when a large number of piston rings 1 are mounted on the piston 81, only the piston ring 1 located on the highest pressure side functions, and only this piston ring 1 is worn. There is a risk.

  Therefore, the low-pressure groove 642 of the second ring 6 of the present embodiment opens from the end face that faces the joint 60 of the second ring 6 as shown in FIG. Specifically, the low-pressure groove 642 opens from one end face 67 whose one end in the length direction faces the joint 60, and the other end in the length direction opens from the other end face 67 facing the joint 60. That is, both ends of the low-pressure groove 642 in the length direction are open to the joint 60 side of the second ring 6.

  The intermediate portion 646 in the length direction of the low pressure groove 642 has a groove width wider than both end portions 647, and the protrusion 52 of the first ring 6 is fitted only in the intermediate portion 646 of the low pressure groove 642. Yes.

  In the piston ring 1 of the present embodiment, the joint 60 of the second ring communicates with the joint 50 of the first ring 5 via the low pressure groove 642. For this reason, the gas on the high pressure side slightly leaks out from the joint 60 of the second ring to the low pressure side through the low pressure groove 642 and the joint 50 of the first ring 5. Therefore, when a large number of piston rings 1 are attached to the piston 81, the large number of piston rings 1 can be evenly worn, and the life of the piston ring 1 can be extended.

  Further, when the piston ring 1 is worn, the joint 50 of the first ring 5 and the joint 60 of the second ring 60 are opened. However, in this embodiment, since the high-pressure side gas leaks out to the low-pressure side via the low-pressure groove 642, the amount of gas leakage can be stabilized regardless of the opening amount of the joints 50 and 60. In addition, for example, the amount of gas leakage can be easily controlled by adjusting the groove width at both ends in the length direction of the low-pressure groove 642.

  In the present embodiment, both end sides in the length direction of the low pressure groove 642 are opened to the joint 60 side, but only one end side in the length direction of the low pressure groove 642 is opened to the joint 60. Good.

  In each of the above embodiments, the piston ring structure of the present invention is applied to the piston ring 1 of the high-stage compression unit 8 in the two-stage reciprocating compressor 2, but the low-stage in the two-stage reciprocating compressor 2 is used. You may apply to the piston ring of the compression part 7 in the side compression part 7, and the compression part piston ring in reciprocating compressors other than a two-stage type.

  Moreover, although each said embodiment demonstrated the example which provided the piston ring 1 in the compressor, the piston ring 1 of this invention may be provided in a piston engine.

DESCRIPTION OF SYMBOLS 1 Piston ring 2 Reciprocating compressor 5 1st ring 50 Joint 52 Protrusion 512 Pressed surface 6 2nd ring 60 Joint 641 Pressure surface 642 Low pressure groove 644 One end part of a low pressure groove 645 Other end part of a low pressure groove 80 Cylinder 802 Compression chamber 81 Piston 810 Ring groove

Claims (4)

  A first ring and a second ring which are arranged to overlap in the piston axial direction, wherein the second ring is arranged on the high pressure side of the first ring in the piston axial direction; A pressed surface that approaches the second ring side in the piston axial direction as it goes radially outward facing the second ring, and the second ring contacts the pressed surface facing the first ring. A piston ring comprising: a pressing surface that approaches the first ring side in the piston axial direction as it goes radially inward, and a low-pressure groove that leads to a joint of the first ring is formed on the pressing surface.   The piston ring according to claim 1, wherein a protrusion to be fitted into the low pressure groove is formed on the pressed surface.   The low-pressure groove extends in the circumferential direction of the second ring, and both end portions thereof are formed so as not to open from both end faces facing the joint of the second ring. Piston ring.   4. A reciprocating compressor that compresses gas sucked into a compression chamber of a cylinder with a piston in the cylinder, wherein a ring groove is formed on an outer peripheral surface of the piston, and the ring groove is any one of claims 1 to 3. 2. A reciprocating compressor comprising the piston ring according to claim 1, wherein the second ring of the piston ring is disposed on the compression chamber side of the first ring.

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